Implementing Kubernetes Pod Security Standards

Overview

Pod Security Standards (PSS) define three levels of security policies -- Privileged, Baseline, and Restricted -- enforced by the Pod Security Admission (PSA) controller built into Kubernetes 1.25+. PSA replaces the deprecated PodSecurityPolicy and provides namespace-level enforcement with three modes: enforce, audit, and warn.

When to Use

• Deciding whether a namespace or workload belongs at Privileged, Baseline, or Restricted
• Auditing which existing workloads would be rejected if Restricted were enforced today
• Translating a "must meet Restricted" requirement into concrete securityContext changes
• Planning a PodSecurityPolicy migration and predicting what will break before it does
• Mapping pod security posture to a compliance control (NIST PR.PS-01, CIS Kubernetes)

Not this skill: configuring the controller that enforces these profiles — namespace labels, AdmissionConfiguration, exemptions, or debugging a pod PSA rejected. Use implementing-pod-security-admission-controller.

Prerequisites

• Kubernetes cluster 1.25+ (PSA GA)
• kubectl configured with cluster-admin access
• Understanding of Linux capabilities and security contexts

Core Concepts

Three Security Profiles

Three Enforcement Modes

Workflow

Step 1: Label Namespaces for PSA

# Restricted namespace - production workloads
apiVersion: v1
kind: Namespace
metadata:
  name: production
  labels:
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/enforce-version: latest
    pod-security.kubernetes.io/audit: restricted
    pod-security.kubernetes.io/audit-version: latest
    pod-security.kubernetes.io/warn: restricted
    pod-security.kubernetes.io/warn-version: latest

# Baseline namespace - general workloads
apiVersion: v1
kind: Namespace
metadata:
  name: staging
  labels:
    pod-security.kubernetes.io/enforce: baseline
    pod-security.kubernetes.io/enforce-version: latest
    pod-security.kubernetes.io/audit: restricted
    pod-security.kubernetes.io/audit-version: latest
    pod-security.kubernetes.io/warn: restricted
    pod-security.kubernetes.io/warn-version: latest

# Privileged namespace - system components only
apiVersion: v1
kind: Namespace
metadata:
  name: kube-system
  labels:
    pod-security.kubernetes.io/enforce: privileged
    pod-security.kubernetes.io/enforce-version: latest

Step 2: Apply Labels to Existing Namespaces

# Apply restricted enforcement to production
kubectl label namespace production \
  pod-security.kubernetes.io/enforce=restricted \
  pod-security.kubernetes.io/audit=restricted \
  pod-security.kubernetes.io/warn=restricted \
  --overwrite

# Apply baseline to staging with restricted warnings
kubectl label namespace staging \
  pod-security.kubernetes.io/enforce=baseline \
  pod-security.kubernetes.io/audit=restricted \
  pod-security.kubernetes.io/warn=restricted \
  --overwrite

# Check labels on all namespaces
kubectl get namespaces -L pod-security.kubernetes.io/enforce

Step 3: Create Compliant Pod Specs

# Restricted-compliant deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: secure-app
  namespace: production
spec:
  replicas: 3
  selector:
    matchLabels:
      app: secure-app
  template:
    metadata:
      labels:
        app: secure-app
    spec:
      automountServiceAccountToken: false
      securityContext:
        runAsNonRoot: true
        runAsUser: 65534
        runAsGroup: 65534
        fsGroup: 65534
        seccompProfile:
          type: RuntimeDefault
      containers:
        - name: app
          image: myregistry.com/myapp:v1.0.0@sha256:abc123
          ports:
            - containerPort: 8080
              protocol: TCP
          securityContext:
            allowPrivilegeEscalation: false

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